首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   345篇
  免费   18篇
  国内免费   9篇
妇产科学   38篇
基础医学   59篇
口腔科学   3篇
临床医学   5篇
内科学   39篇
皮肤病学   1篇
神经病学   12篇
特种医学   16篇
外科学   20篇
综合类   36篇
预防医学   28篇
眼科学   35篇
药学   50篇
中国医学   27篇
肿瘤学   3篇
  2024年   2篇
  2023年   2篇
  2022年   4篇
  2021年   18篇
  2020年   8篇
  2019年   9篇
  2018年   9篇
  2017年   5篇
  2016年   2篇
  2015年   8篇
  2014年   25篇
  2013年   25篇
  2012年   26篇
  2011年   23篇
  2010年   23篇
  2009年   14篇
  2008年   13篇
  2007年   5篇
  2006年   15篇
  2005年   7篇
  2004年   19篇
  2003年   13篇
  2002年   12篇
  2001年   8篇
  2000年   18篇
  1999年   9篇
  1998年   6篇
  1997年   5篇
  1996年   6篇
  1995年   6篇
  1994年   3篇
  1992年   3篇
  1991年   1篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   4篇
  1978年   1篇
  1976年   1篇
  1975年   2篇
  1974年   2篇
  1971年   1篇
排序方式: 共有372条查询结果,搜索用时 15 毫秒
1.
目的研究并比较不同规格怀牛膝不同极性部位的HPLC指纹图谱,探索其内部质量差异,为该药材的规格标准完善及临床用药提供参考。方法将怀牛膝用体积分数75%乙醇水浴回流提取,得体积分数75%乙醇回流提取物,用40 mL水溶解后,依次用石油醚、三氯甲烷、乙酸乙酯、正丁醇进行萃取,得到各萃取相及萃取后的水相,浓缩至浸膏,采集各部位HPLC指纹图谱;运用相似度、综合聚类法进行数据分析,同时对其不同部位的指纹图谱进行比对分析。结果石油醚、氯仿部位均标定了11个共有峰,乙酸乙酯部位标定了10个共有峰,正丁醇部位标定了19个共有峰,水部位标定8个共有峰;氯仿部位指纹图谱相似度差异较大,其他部位指纹图谱相似度差异较小,均在0.9以上;石油醚部位指纹图谱差异主要体现在峰高,乙酸乙酯部位、氯仿部位、水部位的化学成分种类及峰高均存在差异;综合聚类分析能将不同规格怀牛膝区分开。结论不同规格怀牛膝内部质量存在差异;实验中所建立的HPLC指纹图谱可以全面反映不同规格怀牛膝的化学成分分布,为不同规格怀牛膝的整体质量评价提供参考。  相似文献   
2.
L. Abrahamsson  H. Hackl 《Maturitas》1981,3(3-4):225-234
53 patients from a mainly climacteric population were treated monthly with 200 mg dehydro-epiandrosterone (DHEA) oenanthate or with 1 ampoule Gynodian-Depot®. Pronounced adiposity was present in 15 of these cases. Hormonal variables were determined before the treatment and during the depot effect of the preparations in order to study the principle which supports the oestrogenic influence and any weight-reducing influence under administration of DHEA. The elimination of lowpolar oestrogens increased considerably in 4 out of 13 post-menopausal cases treated with DHEA. This effect is probably indirect and presupposes intact ovaries. The incorporation of exogenous DHEA into the excretion of 17-ketosteroids and of 17-ketogenic steroids, such as those of androsterone + aethiocholanolone, depends on the size of the initial pool inasmuch as it is higher in small initial pools than in saturated pools - the size of the pool being age-dependent.

An average weight loss of >1 kg/mth was observed under DHEA treatment in 7 out 15 adipose cases. In comparison to the other 8 adipose cases, these 7 were younger and therefore also displayed higher values for 17-ketosteroids and their individual fractions. These circumstances appeared to explain why the administration of DHEA resulted in higher levels of free plasma DHEA which, in contrast to the cases without loss of weight, also resulted in an increase of renal DHEA-sulphate clearance. It was concluded from the findings that this is the explanation for the catabolic effect of exogenous DHEA.

Post-menopausally increased FSH and LH fractions were markedly suppressed in about half of the determinations after Gynodian-Depot administration, the findings indicating that DHEA is probably involved in suppression of the LH fraction.  相似文献   

3.
目的评价两步活检一、二极体对小鼠卵母细胞体外受精(IVF)和相应胚胎发育的影响。方法8~12周龄雌、雄昆明小鼠。雌鼠促排卵,取成熟卵母细胞行卵胞浆内单精子注射(ICSI),序贯培养胚胎至囊胚孵出。分别于ICSI后激光透明带打孔活检第一极体,两步活检一、二极体,在受精后打孔同时活检一、二极体。比较各处理组与对照组受精、卵裂、优质胚胎、囊胚形成、扩张和孵出情况。结果两步活检一、二极体和同时活检一、二极体受精率、卵裂率、优质胚胎率和囊胚形成率与对照组均无明显差异。启动孵出率明显高于对照组;完全孵出率虽高于对照组,但无统计学意义。结论一、二极体活检不影响小鼠卵母细胞IVF和相应胚胎发育,而且可能有助于胚胎孵出,是安全可行的植入前遗传学诊断(PGD)活检取材方法,以两步活检法为最佳极体活检方案。  相似文献   
4.
Objective: A single oral dose of paracetamol (20 mg · kg−1) was given to 38 Chinese patients with non-insulin-dependent diabetes mellitus (NIDDM) who had either normal renal function or varying degrees of renal impairment, with creatinine clearances ranging from 4 to 123 ml · min−1 · 1.73 m−2. The plasma and urinary concentrations of paracetamol and its major metabolites were measured by high-performance liquid chromatography (HPLC). Results: The absorption and elimination of paracetamol were unaffected by renal impairment. However, the area under the plasma concentration time curve and the elimination half-life of paracetamol metabolites increased significantly with worsening renal insufficiency. Mean renal clearances of paracetamol and its conjugates were significantly reduced in these subjects. There was no evidence of altered metabolic activation with renal impairment. Conclusion: The results demonstrate that paracetamol disposition is minimally affected by diabetic nephropathy; however, extensive accumulation of conjugates may occur. Received: 2 September 1996 / Accepted in revised form: 11 December 1996  相似文献   
5.
During growth of the blastocyst there is a net flow of cells from the polar to the mural trophectoderm which is presumed to be radially symmetrical. However, such a pattern of cell movement is inconsistent with findings from a recent clonal analysis. To visualize the overall flow of cells directly, the polar trophectoderm of expanding blastocysts was labelled globally with fluorescent microspheres. Following further growth, the great majority of blastocysts that remained labelled throughout the polar trophectoderm exhibited a polarized rather than radial spread of label into the mural region. This was the case regardless of the labelling technique, whether the blastocysts were grown in utero or in vitro, or had the zona pellucida removed or left on. Intriguingly, where there were two foci of spread of label into the mural trophectoderm rather than one, these were diametrically opposite each other. In further experiments, fluorescent lineage labels were used to distinguish junctional trophectoderm cells with and without an extension onto the blastocoelic surface of the inner cell mass. The location of clones formed following further blastocyst growth provided no evidence that egress of cells from the polar trophectoderm is restricted circumferentially by the presence of junctional cells having an extension.  相似文献   
6.
BACKGROUND: Attempts to 'rescue' by ICSI oocytes that remained unfertilized 24 h after conventional IVF have generally resulted in poor outcomes. The aim of the present study was to compare the outcome of rescue ICSI performed on one group of patients 6 h after initial insemination with those of another group where rescue ICSI was performed 22 h after initial insemination. METHODS: Twenty-five patient IVF cycles provided the oocytes for rescue ICSI 6 h after initial insemination, and 20 cycles provided the oocytes for rescue ICSI 22 h after initial insemination in this retrospective study. Fertilization and cleavage rates, embryo quality, implantation, and pregnancy rates after rescue ICSI were the main outcome measures. RESULTS: A fertilization rate of 70.3% was achieved with 6 h rescue ICSI compared with 48.5% with 22 h rescue ICSI (P < 0.0001). From 6 h rescue ICSI, 12 clinical pregnancies (48.0%) resulted in three sets of twins, eight singletons and one abortion. From 22 h rescue ICSI there was one (5.0%) singleton pregnancy and delivery of a healthy baby. Likewise, the implantation rate was 20.2% from 6 h rescue ICSI compared with 1.72% from 22 h rescue ICSI (P < 0.02). CONCLUSIONS: Rescue ICSI after 6 h post-insemination (46 h post-HCG) gave better fertilization, pregnancy and implantation rates compared with rescue ICSI after 22 h when oocytes have become aged.  相似文献   
7.
CORDIC算法在B超数字扫描变换器中的应用   总被引:1,自引:0,他引:1  
数字扫描变换器在B型超声诊断仪的应用,能使现代实时B型超声诊断仪实现一些新的诸如图像冻结、多帧贮存、数据测量计算和TV显示等功能。在设计B型超声诊断仪中数字扫描变化器的过程中,直角坐标到极坐标变换是一个关键的技术,本研究论述了应用在数字扫描变化器中的一种新的算法——CORDIC算法,对该算法的原理进行了简介,将CORDIC算法应用到直角——极坐标变换中,并进行了算法修正和公式计算。根据其具体的应用对该算法进行了优化,并给出了算法的硬件实现结构。最后,对算法进行了软件仿真,并给出了结果分析。  相似文献   
8.
目的 揭示两性分子与有序磷脂膜的作用模式。方法 分别使用磷脂膜色谱和正辛醇 水系统测定药物的膜亲和性和疏水性参数。结果 两性分子与有序磷脂膜存在吸引性极性附加作用力 ,其测定的膜亲和性参数要明显比由疏水性参数预测的值高。结论 结合两性分子复杂的微观质子平衡 ,不仅其中性、阳性而且两性的微观离子可能通过匹配的构象和能量有利的作用模式而有效的分布到有序的两性磷脂膜中 ,并且后两者的分配产生了与有序磷脂膜的吸引性极性附加作用力  相似文献   
9.
用全染色体涂抹探针进行卵母细胞第一极体荧光原位杂交   总被引:1,自引:0,他引:1  
 【目的】建立用全染色体涂抹探针(WCP)对卵子第一极体进行荧光原位杂交(FISH)检测染色体的方法。【方法】收集单精子卵胞浆内注射(ICSI)中不成熟卵母细胞经体外培养成熟和常规试管婴儿(IVF)中未能成功受精的成熟卵母细胞,活检第一极体,固定后行13、14号染色体的全染色体涂抹探针荧光原位杂交。活检后,一部分卵母细胞固定行FISH以分析卵子自身的13、14号染色体,其余行ICSI受精,观察受精和卵裂情况。【结果】共获得成熟母细胞93个,成功活检85个,成功固定78个,共29个第一极体处于分裂中期,均有FISH结果。卵母细胞体外培养成熟后立即取极体进行固定,90.5%(19/21)的极体处于分裂中期,而取卵后30-48h和72h后活检的第一极体处于分裂中期的比例分别为27.3%(6/22)和11.4%(4/35),3组相比有统计学差异(P〈0.01)。11个卵母细胞同时获得了极体和相对应卵细胞的FISH结果,其中10个极体和相对应的卵细胞分别有1条13,14号染色体,剩余1个卵母细胞的极体有2条14号染色体和1条13号染色体,相对应的卵细胞仅有1条13号染色体,二者互补。活检后行ICSI受精的卵母细胞受精率为78.6%(11/14),优质胚胎率45.5%(5/11)。【结论】全染色体涂抹探针对卵子第一极体进行遗传分析可以有效、准确地推测相对应卵母细胞的染色体构成,从而应用于女性染色体易位患者的植入前遗传诊断。  相似文献   
10.
Neurotherapeutic potentials of Centella asiatica and its reputation to boost memory, prevent cognitive deficits and improve brain functions are widely acknowledged. The plant's bioactive compounds, i.e. asiaticoside, madecassoside and asiatic acid were reported to have central nervous system (CNS) actions, particularly in protecting the brain against neurodegenerative disorders. Hence, it is important for these compounds to cross the blood-brain barrier (BBB) to be clinically effective therapeutics. This study aimed to explore the capability of asiaticoside, madecassoside and asiatic acid to cross the BBB using in vitro BBB model from primary porcine brain endothelial cells (PBECs). Our findings showed that asiaticoside, madecassoside and asiatic acid are highly BBB permeable with apparent permeability (Papp) of 70.61 ± 6.60, 53.31 ± 12.55 and 50.94 ± 10.91 × 10?6 cm/s respectively. No evidence of cytotoxicity and tight junction disruption of the PBECs were observed in the presence of these compounds. Asiatic acid showed cytoprotective effect towards the PBECs against oxidative stress. This study reported for the first time that Centella asiatica compounds demonstrated high capability to cross the BBB, comparable to central nervous system drugs, and therefore warrant further development as therapeutics for the treatment of neurodegenerative diseases.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号